This is a model of language evolution, where agents are human populations that possess a dialect. A dialect is modelled here as simply an ordered two array of ones and zeros. One of these arrays is the 'core' of the dialect; it is smaller but more important, and as such plays a greater role in determining mutual intelligibility as well as having a slower mutation rate.

HOW IT WORKS

Two dialects are considered variants of the same language if they are mutually intelligible. Otherwise they are different languages.

HOW TO USE IT

Mutation rate is how fast dialects change on their own. Borrow rate is how fast they are influenced by neighbouring, mutually intelligible dialects. Mutual intelligibility ratio is how similar two dialects must be for one to say they can understand the other.

THINGS TO NOTICE

If two agents have the same dialect, they will be the same colour. However, two agents with the same colour may or may not have the same dialect. The dialect core plays a disproportionate role in determing the agent's colour, though, so it is more likely than not that agents of the same colour have mutually intelligible dialects.

Calculating language diversity is somewhat intense computationally and can cause the program to stall momentarily. For this reason a switch and slider are provided to allow you to plot this value less often or not at all.

THINGS TO TRY

Try drawing boundaries by clicking on that button and then clicking and dragging on the world. You can draw them first and then populate the world, or populate first and then draw accordingly.

EXTENDING THE MODEL

Each agent could take its mutation/borrowing/etc rate as some multiple of the global parameter; the dialect could be modelled with numbers between 0 and some number much higher than 1; an agent could convert wholesale to a neighbour's dialect, even if it is not mutually intelligible to its own; and so on...

NETLOGO FEATURES

This model provided some good exercise in working with lists, the NetLogo equivalent of arrays.

RELATED MODELS

Genetic Drift - "GenDrift T interact" is similar in many respects

CREDITS AND REFERENCES

Made by Chuck Cranston for a class taught by Dr Jeff Fletcher at Portland State University, fall 2009.